Over the last twenty years, off-road vehicle recreational activities have become increasingly popular. The number of off-road sporting events and rock crawling competitions has increased. Tires suitable for such events are typically heavily lugged tires, with large spacing for improved traction and a high number of biting surfaces to enable the tire to both grip the uneven terrain and to throw out any mud. Those tires used almost exclusively for such sporting events are manufactured with an enhanced construction to improve durability under severe conditions.
Because of the popularity of such events, the look of the off-road tire has transitioned into use for conventional vehicle use. Light truck and passenger vehicle tires with a more rugged look have become increasingly popular and when mounted on light trucks and SUV's enable the operator to drive in limited off-road conditions and to participate in off-road recreational activities. The widely spaced lugs of such tires increases the possibility of punctures and cuts in the unprotected under-tread and shoulder areas of the tire. In some applications, operators will reduce inflation pressures to further improve the off-road traction. However, this causes the tire to bulge in the shoulder areas, exposing those areas of the tire to further risk of puncture.
To decrease the risk of punctures and cuts, current methods include increasing the under-tread gauge, increasing the net-to-gross ratio of the tread, adding plies and belts to the carcass, or using new rubber compounds. These methods not only increase the weight and cost of the tire but also limit off road performance.
BFGoodrich's Mud-Terrain and Krawler tires are designed for off-roading activities, and have defined by larged lugged treads. The shoulders of tire tires are defined by multiple biting edges. However, the shoulder lugs are widely spaced, creating the risk of punctures and cuts. In an apparent attempt to eliminate such problems, every other shoulder groove of the Krawler and every shoulder groove of the Mud-Terrain has a very thin rib in the base of the groove. This very thin rib is also located in the tread shoulder. However, due to the thickness and width of the rib, a large portion of the groove remains exposed to the elements and the edges of the adjacent lugs are still exposed to cuts and tearing.